When an insufficient amount of refrigerant is circulated through the refrigerant compressor of the refrigeration system of an air conditioner due to, for example, leakage of the refrigerant from the system, not only the refrigeration system will be starved but, the refrigerant temperature in the cooling cycle with respect to a thermal load rises, and in particular a refrigerant suction and discharged fluid temperature will rise. The insufficient lubrication results from leakage of the lubricant contained in the refrigerant being allowed to leak from the refrigeration system.
The present invention contemplates provision of a device adapted to stop the refrigerant compressor or produce a warning signal in the event the temperature in the refrigerant compressor raises beyond a predetermined critical value due to the lack of refrigerant passed through the compressor.